[JWOLIN]

First off I have a 98 Vette, the car is highly modified to include an engine swap from a LS1 to a Supercharged LS6. About a year ago I started to loose fuel pressure during a heavy load / hard acceleration. "Not a good thing on a supercharged car". it would seem that if I give the car full throttle my fuel pressure will actually drop to zero and I believe this to be a true reading for several reasons. #1 the car looses a considerable amount of power, I've ohmed the fuel pressure sending unit and its fine, my last 255lpm fuel pump was getting loud so I changed that out for a new one in addition I have a fuel boost-a-pump as well which I'm sure most of you know is nothing but a vacuum actuated voltage capacitor so to speak. New pump no change, new boost-a-pump no change, replaced the TPS, MAP, replaced the fuel pressure regulator, disconnect the vacuum line to the fuel pressure regulator no change, I have no engine codes that relate to this issue, just the typical C5 P1571 and P1644 TPS codes.

The unfortunate side to this is that I have spent a ton on money trying to figure out this issue at all sorts of Tuner, and Dyno shops with no good results or a cause for this issue. I don't go to dealers for fear they will erase my tuning from the PCM, they already did it once to me and I got stuck paying to re-tune and dyno the car.

Any assistance any of you could offer would be greatly appreciated.

 

[T.M.]

you sound like you know about your own car, so i am not going to question your pump install, filter? Maybe something happen to the supply line somewhere, a rock or something maybe kinked or pinched the line somewhere? Does it seem to matter if the tanks are almost empty or full? Injectors good? Do you have a scanner?

 

[JWOLIN]

Done it, checked the line's for obstruction and replaced the fuel filter. I regularly change the filter about every 7,000 miles but I put a new one on with the pump.

you have a really good point with a pinched line or dented, that thought never even crossed my mind, I had always assumed the fuel lines were routed through the cars body.

Was also thinking about the relay in the K harness for the steering wheel lock, that also controls the fuel voltage signal.

Ok here is the strangest part, In first gear I don't loose fuel pressure at wot although the car winds up to 6100 almost instantaneously, 2nd gear I dont show a drop in pressure either but on occasion the loss of power is apparent, 3rd hear it happens every time WOT and the pressure drops every time.

empty or full doesent matter, and my injectors are in very good shape.

 

[T.M.]

As far as the kinks, i was visualizing something rite around the engine or near by. Good point on the replay, but im thinking the psi would be consistantly low. Sounds like theres enough pressure at idle, might be that as you take off, it just takes a few seconds ( 1st & 2nd gear) to bleed the pressure off the line, maybe the new pump is defective? Could do a caveman style flow test, might not be totally accurate, but put the engine side fuel line in a 5 gal gas can, seal the top so no splash or spillage, then run the fuel pump and see if its flowing alot of gas. Theres a certain amount the can should fill up in 1 minute, but i dont have my fuel injection book with me at work.'

 

[JWOLIN]

It was doing this also with the old fuel pump, I figured well the pump was getting loud because it was wearing out & thought oh this will fix the issue. ( NOT )Both pumps are the Lingenfelter 255lpm so its easy to tell if it's flowing enough with a at home can test.

I was also thinking of running a hot wire to the pump from a constant 12v source on a toggle switch in the cab to see if that has any effect, with a switch on it should hold pressure from a constant 12v source if that turns out to solve the issue then i know the problem is electrical. Of not them it's a programming or flow issue.